The present invention relates to electromagnetic filters and methods of providing electromagnetic filters.
It is known in the prior art to use an inductor and a capacitor circumferentially disposed about a feedthrough conductor in order to filter unwanted electromagnetic energy from a signal being carried by the conductor. In some prior art devices, the capacitor is circumferentially disposed about the inductor, and the inductor is circumferentially disposed about the conductor. Such an arrangement provides a compact filter, but the electromagnetic characteristics of that filter may be dictated by the reactance intrinsic to the ground design.
Also in the prior art is the use of discoidal capacitors, circumferentially disposed about a feedthrough conductor. When used in combination with an inductor, the discoidal capacitors are set apart from the inductor, and this increases the size of the electromagnetic filter.
The invention may be embodied in an electromagnetic filter for use with a feedthrough conductor. An inductor having a metallized surface is disposed about the conductor, and a capacitor is joined to the inductor. A first conductive contact electrically connects one set of capacitor plates to the metallized surface and a second conductive contact electrically connects another set of capacitor plates to the feedthrough conductor.
The invention may be embodied in a method of providing an electromagnetic filter. An inductor may be provided, and coated to provide a metallized surface. A capacitor is electrically connected to a first conductive contact and a second conductive contact. The capacitor may be joined to the inductor and the first conductive contact may be electrically connected to the metallized surface. The second conductive contact may be joined to the feedthrough conductor.